The existing disconnecting switches use motor-type driving devices to directly drive insulated revolving shaft to operate crank at high-voltage side, so as to perform switch-on/switch-off operations through the crank. For example, 123-550KV scissor-type disconnecting switch manufactured by ALSTOM (China) Investment Co., Ltd. has such structure. Since this type of disconnecting switch uses motor direct drive mode, the speed is relative slow when the motor just starts up, and then the speed gradually increases. However, the switch requires relative high separating speed when performing switch-on/switch-off operations. No matter it is motor direct drive type or other types of mechanical direct drive disconnecting switches, the above deficiencies are inevitable. In addition, the two cranks of the scissor-type disconnecting switch perform relative movement through synchronous opposite rotation of two directly engaged gears. Due to the space between the two gears is too small, the maximum turning angle for the two cranks is 90 degree. When the two cranks clamp the bus, they may tend to open towards sides, and may upwardly impact the bus upon mobile contact on top of the crank touches fixed contact. This will affect the service life and stability of the mechanism.